1. Field of the Invention
The present invention relates to motor control devices that drives and controls a motor, and more particularly to a motor control device that contributes to the reduction of vibration associated with the driving of the motor.
2. Description of Related Art
When permanent-magnet synchronous motors are used, it is necessary to use a technology for reducing vibration, including the radial vibration of the stator of the motor. The radial vibration of the stator is the vibration in the direction of the radius of the motor, which is caused by the magnetic attractive force exerted between the permanent magnet provided on the rotor of the motor and the stator. The radial vibration of the stator is transmitted to a frame (unillustrated) that holds the stator. This causes the frame to vibrate, resulting in the generation of noise. In particular, mechanical structural members such as the stator and the frame vibrate sympathetically at a particular rotation speed, causing strong vibration and noise. It is for this reason that reducing the radial vibration is of critical importance.
Accordingly, various methods have conventionally been proposed to reduce the vibration of the motor.
For example, a method has been proposed that reduces the vibration caused by torque pulsation by passing a d-axis current at regular intervals by referring to variations in the load torque.
There has also been proposed a method that reduces the vibration caused by cogging torque.
Additionally, there has been proposed a method that aims to reduce the vibration by superposing a harmonic on a multiphase alternating current.
As described above, reducing the radial vibration is of critical importance, and accordingly a method that can effectively reduce the radial vibration is keenly sought after. As well as reducing the radial vibration, reducing all the vibrations associated with the driving of the motor is an important goal to be achieved.